The present invention relates to a sputtering target for use in forming thin films of semiconductor devices. In particular, the present invention relates to a metal sputtering target integrated with a backing plate, and a method of producing the same. The term “metal target” includes targets made from metal and made from alloy. In particular, in the case of a titanium target, this includes a titanium alloy target.
In recent years, film deposition is being performed for various electronic components by using metal or alloy sputtering targets. In particular, the use of titanium (titanium alloy) sputtering targets is increasing.
Generally speaking, a sputtering target is often bonded with a backing plate by using a bonding material or the like, and after using the target, it is necessary to stop the sputtering equipment to replace the spent target with a new one. Nevertheless, this downtime deteriorates the production efficiency.
Thus, in order to shorten the downtime as much as possible and reduce the manufacturing cost, there are demands for producing a target integrated with a backing plate in order to increase the thickness of the target itself. Nevertheless, this type of integrated target has a drawback in that, because the mechanical strength is insufficient, the target is subject to deformation such as warping during the sputtering process.
In order to resolve this kind of drawback, for instance, Patent Document 1 discloses a technology of producing an integrally-structured target in which the target and the backing plate are produced with the same material, wherein, by subjecting the target to plastic working in order to increase the mechanical strength, the target will not be subject to warping or other deformation even when sputtered at a high power.
Nevertheless, when the plastic working conditions are changed in order to increase the mechanical strength of the overall target, the sputtering properties of the target itself will change, and there is a problem in that the intended product performance cannot be satisfied.
Patent Document 2 describes a technology of causing the non-erosion portion of the sputtering target to be irradiated with a laser so as to form a recess, and causing the hardness of the bottom face of such recess to be smaller than the hardness of the surface of the non-erosion portion in order to prevent the generation of coarse particles. Nevertheless, since this technology softens the melt portion via laser irradiation and causes the hardness of the bottom face of the recess to be smaller in comparison to the hardness of the surface of the non-erosion portion, Patent Document 2 does not aim to inhibit the deformation of the target during sputtering by increasing the strength of the target.
Patent Document 3 provides an aluminum or aluminum alloy sputtering target and a method of producing such a target. Pure aluminum or aluminum alloy is mechanically processed into a round blank, and the blank is subject to recrystallization heat treatment in order to realize the required crystal grain size and crystal texture. After this heat treatment step, additional strain of 10 to 50% is applied to the blank in order to increase the mechanical strength. Furthermore, strain in the flange area of the target is larger than the strain in the other target areas, and strain is applied to the flange area at a ratio of approximately 20 to 60%. Subsequently, the blank is subject to finishing processing to obtain a sputtering target possessing the required crystal texture and sufficient mechanical strength.
Patent Document 4 describes a backing plate-integrated sputtering target in which the Vickers hardness Hv of the flange part is 90 or more, and the 0.2% yield stress of the flange part is 6.98×107 N/m2 or more.
While foregoing Patent Document 3 and Patent Document 4 describe a backing plate-integrated sputtering target, since their production conditions require the flange part to be simultaneously subject to plastic working, strain is applied from the periphery to the center part of the target pursuant to the plastic working of the flange part, and there is a problem in that there may be variations in the hardness of the target.
Patent Document 1: JP 2002-121662 A
Patent Document 2: JP H09-209133 A
Patent Document 3: JP 2012-515847 A
Patent Document 4: International Publication No. WO 2013/047199